Scientists find Active thermite residue in WTC dust

http://www.nytimes.com/2003/12/03/n...07&en=a2c62eb2b42cf30c&ex=1385874000&adxnnl=1

December 3, 2003
New Evidence Is Reported That Floors Failed on 9/11
By JAMES GLANZ

GAITHERSBURG, Md., Dec. 2 ? Federal investigators said here Tuesday that new evidence supported earlier suggestions that the floor supports in the World Trade Center began failing in the minutes before the towers fell and might have played a major role in their collapse.

The investigators, who are carrying out a two-year, $16 million analysis of the collapses, made it clear that they had not yet settled on a final explanation. They said, though, that their findings gave new weight to a theory that the failure of the floors weakened the towers' internal structure to the point that the entire buildings came down.

S. Shyam Sunder, who is leading the investigation for the National Institute of Standards and Technology in the Commerce Department, said, "We are seeing evidence of floors appearing to be sagging ? or that had been damaged ? prior to collapse." Still, Dr. Sunder said, "The relative role of the floors and the columns still remain to be determined in the collapse."

According to an alternative theory of the collapse, the planes that smashed into the towers damaged the towers' vertical structural columns so severely that the buildings were virtually certain to fall. In that view, none of the buildings' many structural novelties ? the towers were daring engineering innovations in their day ? would have played a significant role in the collapses.

Last spring, the standards institute found the first photographic evidence on the east face of the south tower that a single floor ? with its lightweight support system, called a truss ? had sagged in the minutes before it started collapsing. Now, detailed analysis of photos and videos has revealed at least three more sagging floors on that face, said William Pitts, a researcher at the institute's Building and Fire Research Laboratory.

In addition, Dr. Pitts said, sudden expansions of the fires across whole floors in each tower shortly before they fell suggested internal collapses ? burning floors above suddenly giving way and spreading the blaze below.

Finally, an unexplained cascade of molten metal from the northeast corner of the south tower just before it collapsed might have started when a floor carrying pieces of one of the jetliners began to sag and fail. The metal was probably molten aluminum from the plane and could have come through the top of an 80th floor window as the floor above gave way, Dr. Pitts said.

"That's probably why it poured out ? simply because it was dumped there," Dr. Pitts said. "The structural people really need to look at this carefully."

The investigators also said that newly disclosed Port Authority documents suggested that the towers were designed to withstand the kind of airplane strike that they suffered on Sept. 11.

Earlier statements by Port Authority officials and outside engineers involved in designing the buildings suggested that the designers considered an accidental crash only by slower aircraft, moving at less than 200 miles per hour. The newly disclosed documents, from the 1960's, show that the Port Authority considered aircraft moving at 600 m.p.h., slightly faster and therefore more destructive than the ones that did hit the towers, Dr. Sunder said.

The towers did withstand the plane strikes at first, allowing thousands of people to escape, but then the fires, stoked by burning jet fuel, softened the steel of the towers. Potentially challenging other statements by Port Authority engineers, Dr. Sunder said it was now uncertain whether the authority fully considered the fuel and its effects when it studied the towers' safety during the design phase.

"Whether the fuel was taken into account or not is an open question," Dr. Sunder said. It is also unclear, he said, "whether the extent of the loss of human life as a result of that" was taken into account.

The studies of the floor trusses and the design of the towers are just two elements of the investigation, which is carrying out computer calculations of the collapses, rebuilding pieces of the towers in order to test them in real fires, and piecing together a highly detailed chronology of the response to the attack.

In one set of laboratory tests concerning the floor trusses, researchers used earthquake simulators to violently shake assemblages much like the ceilings in the twin towers. The shaking was meant to simulate the impact of the aircraft.

The findings, said Richard Gann, a senior research scientist at the Building and Fire Research Laboratory, showed that many of the fire-protecting ceiling tiles near the impact probably crumbled, exposing the undersides of the trusses directly to the fires.

 

Steel at room temperature: 100% Strength

Steel at -50F: 111% Strength

Steel at 500F: 91% Strength

Steel at 900F: 76% Strength

Steel at 1100F: 69% Strength

Steel at 1350F: 44% Strength

Steel at >1700F: <10% Strength.

See a correlation Here??

Ever seen a black smith pounding out steel at 850 degrees? Why does this work?

The confined temperature in the WTC was about 1100 to 1500F.

All it takes is one failure to get a floor falling and nothing will stop it. The momentum is more than the building was built to withstand in perfect order. Drop thirty storeys of a building from 10 feet and see what happens to anything around it or under it.

 

I just wanted to talk a bit about this part. Kinetic energy (the energy an object possesses due solely to its motion, or alternatively the amount of work required to accelerate a given mass--or the work distributed in an objects deceleration) is defined by the equation: KE = 1/2 * (mass) * (velocity)^2.

So the difference between the firewall speed reported by the second plane (~586 mph) and the 600mph is 14mph, or about 6 m/s, and therefore a 4% difference in the calculation. And the Port Authority guess of a 707 (weight ~220,000#) is about half that of a 767-233ER (385,000#). So the work done by the deceleration of the 9/11 flights from 600mph to zero (absorbed almost entirely by the building) was about twice more than the building was designed for by the PA. And that's just the kinetic energy from the airplane. For the calculation, it comes out to about 14 billion joules--or about 3 tons of TNT.

Then you factor in the ~12000 gallons of fuel onboard. Contrary to popular (uninformed?) opinion, since the fuel didn't mix at a high ratio with air before it started burning, there wasn't a large explosion like you see on CHiPs reruns. If there had been an explosion of high-pressure supersonic gases, there would've been a large sonic boom that shattered concrete, and not the long, loud roar consistent with subsonic deflagration. (There were "small" explosions, that occurred most likely when the fire reached a large column of air, like an elevator shaft or something). Since they weren't supersonic gases, they didn't have an expanding shock wave that went through load-bearing supports, but instead passed around the support columns.

The WTC columns were covered with insulation that was designed to maintain their strength for about 2-3 hours of ordinary fire. But it wasn't just office paper and desks that were the cause of the fire--it was aviation fuel. The rate of burning was limited not by lack of fuel, but lack of oxygen in confined spaces. Lower oxygen content means a longer, slower burn. The heat had more time to penetrate the insulation. A little like cooking your steak: if you sear it quickly you'll get crust on the edges and stay almost raw in the center, even at very high temperatures. But if you have it on a long, slow cook, you'll penetrate through the meat and raise the temperature of the inside. In the case of the WTC, the "inside" was the structural steel. And as steel gets hotter, it gets weaker both in tensile strength and modulus of elasticity. (Can't hold up as much, and bends more, causing more weakness) Read this chapter of the "Structure Steel Handbook" by the American Society of Mechanical Engineers, page 1.17ff. Then compare it to the Popular Mechanics report debunking many of these conspiracy theories, including the "can't melt steel with gas" one.

I find it extremely difficult to bend the laws of physics to invent a conspiracy here. The Occam's Razor approach would say that a 100-ton airplane carrying around 12000 gallons of jet fuel would, upon crashing into a high-rise with twice the energy the building was designed for, and igniting hotter fires than expected or designed for, weakening the structural steel to a point where even the engineered design factors put in for safety weren't enough to support the load of 20-40 floors of concrete and steel---it would say that "duh, the building came down b/c 40 floors of concrete and steel, no longer being held up, accelerated toward the ground pretty quickly due to gravitational force. The mass of 40 floors impacting a floor beneath it at the acceleration of gravity would therefore cause a dynamic force to be imparted to the lower floor much much higher than it was designed for, and it would then collapse, starting a chain reaction. You don't have to be a rocket scientist or nuclear physicist to understand it, I hope--but fortunately I am both and hopefully can help.

 

Hahaha.

Nice!

Ed O.

 

The article said the investigation cost $16M over two years. Just what does that buy? Let's look at 1 year and half that amount.

$8M buys...

$40K/month office space = ~$500K (includes electricity, phone, insurance, etc.)

35 top engineers and scientists @ $200K/year each = $3.5M

40 "workers" @ $50K = $2M

Leaves $2M to rent electron microscopes, farm out studies, etc.